The major objective of the proposed research is to define and characterize several of the enzymes and other proteins that are necessary for the synthesis of adenovirus 2 (Ad2) DNA during productive infection in human KB cells. The study will also attempt to define the specific function of each of these enzymes and ancillary proteins. The investigations will involve the use of a soluble, multienzyme DNA synthesizing complex (SMEC) which is isolaed from the nuclei of Ad2 infected KB cells late after infection. This complex carries out authentic in vitro elongation of Ad2 DNA and terminates DNA replication in vitro in a manner that is experimentally indistinguishable from in vivo termination. Since adenovirus employs mostly cellular enzymes for its own replication, this system is proposed as a model for the study of the enzymology and specific processes involved in mammalian DNA replication. The specific aims of the proposed research are: 1. Further analysis of in vitro termination of Ad2 DNA synthesis; 2. Investigation of the attachment of an (early) protein to the termini of Ad2 DNA labeled in vitro; 3. Reconstitution of an "elongation-termination complex" and analysis of its products and enzymology; 4. Reconstruction of an "initiation complex" from purified components; 5. Structural analysis of the DNA labeled in vitro in the soluble complex.